While not limited thereto in its utility, the present invention is particularly well suited for use as a sterilizing process for killing micro-organisms in containers which are intended to receive food-stuffs. Known processes for sterilizing containers in which food stuffs are to be packaged include UV irradiation, treatment with a mixture of steam and air and the so-called wet aseptic technique in which the interior wall of the container is sprayed with a hydrogen peroxide mixture and subsequently dried. Experience has shown peroxide to be a particularly reliable sterilizing agent for killing microorganisms and containers subjected to the wet aseptic technique may accordingly be used when a long shelf life is required.
The germicidal action of peroxide depends upon the formation of free oxygen, the free oxygen being formed during thermal decomposition and exhibiting a particularly strong sterilizing effect at the moment of formation. The efficiency of a wet aseptic process is also attributable to the liquid hydrogen peroxide which penetrates the cell coatings of the microorganisms.
Under the best of circumstances, i.e., with the finest nebulisation, only thirty-five percent of the internal surface of a container can be wetted by an atomized hydrogen peroxide mixture. The inability to completely wet the surface of the container to be treated is attributable to the fact that droplets form on the surface and unwetted areas remain between these droplets.
Since peroxide is a toxic substance, it is necessary to remove substantially all residues of peroxide from containers treated by a wet aseptic process. The removal of the peroxide is achieved by evaporation and thus a wet aseptic process requires, subsequent to the spraying step, a heating step. The combined spraying and heating steps, however, do not result in absolute sterilization of the entire internal surface of a treated container.